Among the parts of a machine, the slidable ones which operate under a relatively high plane pressure usually defy formation of a stable lubricant film and therefore their materials are required to be highly resistant to wear and pitting. Materials presently available are surface-hardened ones including quenched steel with high hardness, chilled cast iron, hard chromium-plated or soft-nitrided steel, but they can not always meet the requirements, many of them suffering troubles like wear or pitting. Meanwhile, in recent years, auto parts are increasingly required to have better performance and longer life. Particularly, there has been strong desire to improve the performance of these slidable parts. Iron base sintered alloys are admittedly excellent in anti-wear property and are found advantageous as materials for slidable parts to serve under a relatively low plane pressure. When applied, however, in service under a high plane pressure, the sintered alloys, which are highly porous, do not permit formation of a stable lubricant film on account of the porosity which absorbs the oil. Besides, they have such a low strength that they are liable to buckle or collapse under a high plane pressure in service and are vulnerable to pitting, which is a result of local fatigue on the surface. For these reasons iron base sintered alloys have seldom been put to use in high plane pressure service.